1. Field of the Invention
The invention relates to optical systems generally, and, in particular, to multi-focus optical systems. One such system would include a bar code scanner that focuses at multiple points and/or in different directions to read bar codes located at different distances or locations from the scanner.
2. Related Art
Bar code scanners that focus at different regions in order to read bar codes at different distances from the scanner have been implemented using different lasers for each region. For example, a first laser is used for scanning bar codes in a first region, closer to the scanner, and a second laser is used for scanning bar codes in a secured region further away from the scanner. A disadvantage of such systems is the expense and complexity of multiple lasers and focusing systems.
The invention herein seeks to provide a more efficient method and apparatus for providing a multi-focus optical system. According to the invention, at least two different focal regions can be made from a single polarized optical beam. According to the invention, light of a first polarization reflects off an element having a first reflective surface. Light of a different polarization passes through the first element and is acted upon differently by a second element. The first and second elements can be integrated into a single optical element. The first element is reflective while the second element may be reflective, transmissive or diffractive depending on a desired effect.
In one embodiment, light of one polarization, for example from a laser, is reflected from an optical element having a polarization coating on a first reflecting surface and light of a second polarization is reflected a second reflecting surface with a curvature different from that of the first reflecting surface. Light of a first polarization reflected from the first reflecting surface produces a focal position different from the focal position of light of a second polarization reflected from the second reflecting surface. When applied to a bar code scanner, bar codes located in either region can be read.